The Southern Seawater Desalination Plant will produce 50 billion litres of drinking water annually with a capacity to expand to 100 gigalitres (GL) per year. At the completion of the project in late 2011, on average, more than 30 per cent of Western Australia’s water supply will come from climate independent sources with the current Perth Seawater Desalination Plant contributing approximately 17 per cent.
The project is being delivered by the Southern Seawater Alliance, led by Spanish companies, Tecnicas Reunidas and Valoriza Agua. Its partners include construction company AJ Lucas and engineering consultancy WorleyParsons. Following construction, Tecnicas Reunidas and Valoriza Agua will operate the 50 GL/a of water plant for a period of 25 years for the Water Corporation of Western Australia.
AJ Lucas General Manager Construction and Infrastructure Ian Redfern said that the company is happy to be constructing the Southern Seawater desalination pipeline through an alliance strategy.
He said “Alliances are collaborative arrangements where parties jointly work together to deliver the outcomes of a project. They are characterised by a risk sharing and a no-disputes regime.”
At its peak, it is expected that a workforce of 500 people will be involved in the project.
The water pipeline, to be constructed by AJ Lucas, will link the desalination plant to the Integrated Water Supply Scheme (IWSS) and other components of the $955 million Southern Seawater project.
The desalination plant will be situated on Taranto Road, between Binningup and Mylaup, 28 km north of Bunbury. Water from the plant will be fed into the IWSS near Harvey, via a new 1.4 m diameter, 30 km pipeline. From there the water will join the existing Stirling Trunk Main taking water from the Stirling Dam into the Integrated Water Supply Scheme.
The pipeline component will also involve the construction of a pump station at Ravenswood. The station will pump up to 120 ML/d of water from the Stirling Trunk Main to the Tamworth Reservoir, and 160 ML/d of water to Serpentine or North Dandalup Dam via the new pipeline.
Environmental conditions
The desalination plant and pipeline are located in an environmentally sensitive area and great care has to be taken to install the pipeline. AJ Lucas will be employing trenchless technology to minimise the impact on the surrounding environment, including the coastal dunal system located along the pipeline route.
AJ Lucas Site Engineering Christopher Freno is overseeing the construction of:
* A shaft on the beachfront;
* Installation of tunnel boring machinery;
* The tunnel(s) required to be bored out to sea and under the seabed; and,
* The installation of the approximately 1 km caisson(s) out at sea to complete the tunnelling process.
Mr Freno said “Obviously it is very technical when any project involves tunnelling under the seabed.”
Geotechnical and ground tests are currently being completed, to test the sand and ensure that water won’t enter the pump station shaft during tunnel construction.
“We’re digging into the sea – we don’t want any mishaps out there. Aside from that it’s a beautiful environment to work in,” Mr Freno said.
The shaft construction and excavation of all chambers is set to commence in October and is due for completion mid-February 2010. Tunnelling works will then commence and are expected to be completed by the end of 2010. Marine works are to commence at the end of 2010.
Marine exclusion zones are to be set up during marine construction and all marine construction works are to temporarily cease if whales or dolphins are sighted within the marine exclusion zone. Marine construction works may only resume when they are outside the exclusion zone.
WA Water Corporation said that preserving as much of the existing vegetation as possible is a key environmental challenge to be faced. The Corporation have attempted to minimise the impact on vegetation by purchasing a disused quarry at the rear of the plant site to house the majority of its infrastructure, thereby significantly reducing its footprint. With significantly less clearing required, the Corporation said that it is able to preserve the habitats for the nationally protected Western Ringtail Possums and the Carnaby Black Cockatoos.
Western Australian Water Minister Graham Jacobs said he was confident all potential environmental impacts could be mitigated.
“The Alliance and the Water Corporation will be part of these communities for the next 25 years and these bodies will always be mindful of the need to be good neighbours and good corporate citizens,” said Mr Jacobs.
WA Water Corporation explained that extensive community and stakeholder consultation has been undertaken. This consultation has provided community members with the opportunity to be involved in the approvals processes and allowed the Water Corporation to gain an understanding of the major community concerns. Consultation will continue throughout construction and operation.
Major community concerns include noise, visual amenity, terrestrial impacts and marine impacts, potential beach closure and the utilisation of a construction camp. Throughout the planning phase the Water Corporation and Southern Seawater Alliance were able to mitigate most of the community’s concerns.
The Water Corporation and the Southern Seawater Alliance said that they will continue to consult with the community as the construction of the project moves forward.
